Really expected you to weigh in on this.

Apologies ... sometimes life interferes ... been a very busy few days 😞 

It appears there is an issue with ffmpeg/ffprobe that is installed on your system.

The static version comes with its own ffmpeg and ffprobe - the shared version uses the ffmpeg/ffprobe version that comes with your system.
The shared version is only there as it is a much smaller distribution, which some prefer (and why wouldn't they if they already have ffmpeg/ffprobe on their system). Not being the most experienced user, half the time I do not know what to expect from the wild and crazy variation of distributions.

As for the location, an experienced Linux user once suggested using "/usr/share/RenameMyTVSeries" (see also the readme.txt), but I always have it somewhere in my home directory (~). Installing in "/" is a bad idea indeed - on any Linux distro. I have no clue what the recommended location would be usable for all Linux distros, well except for a location somewhere in the home directory (me not being an expert). Not sure if "/usr/share/RenameMyTVSeries" is bad under Arch or not.

I think it might be the way you have it linked cause the one thing I didn't do during my test was actually hit rename, cause the files I tested with had already been named properly. The tests were just to see if the drag-and-drop would finally work properly. I say the above cause under Metadata Option the first option says "[DISABLED - ffprobe is missing] Enable FFprobe". Grabbed a new series and none of the files will rename. Tells me renaming failed.

As for ffmpeg working correctly or not it's fine cause I'm able to use both MKVToolNix and Handbrake without issue. I just did a permissions check and other than having a few extra permissions they match what you have in the readme.

-rwxr-xr-x 1 cccp64 cccp64  362696 Jul  2 12:02 ffmpeg
-rwxr-xr-x 1 cccp64 cccp64  206312 Jul  2 12:02 ffprobe
drwxr-xr-x 1 cccp64 cccp64     120 Oct  3 08:24 icons
-rwxr-xr-x 1 cccp64 cccp64    2646 Jun 11  2020 readme.txt
-rwxr-xr-x 1 cccp64 cccp64 5605336 Sep 28 02:44 RenameMyTVSeries
-rwxr-xr-x 1 cccp64 cccp64     375 Jun 11  2020 RenameMyTVSeries.desktop

FAILED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E01.There.Is.No.Line.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E01 There Is No Line.mkv (ERROR: ffMPEG failed to create new file)
SKIPPED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E01.There.Is.No.Line.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E01 There Is No Line.mkv (File not renamed - Renaming original mediafile failed.)
FAILED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E02.Primm.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E02 Primm.mkv (ERROR: ffMPEG failed to create new file)
SKIPPED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E02.Primm.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E02 Primm.mkv (File not renamed - Renaming original mediafile failed.)
FAILED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E03.A.Gig's.A.Gig.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E03 A Gig’s A Gig.mkv (ERROR: ffMPEG failed to create new file)
SKIPPED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E03.A.Gig's.A.Gig.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E03 A Gig’s A Gig.mkv (File not renamed - Renaming original mediafile failed.)
FAILED: /mnt/My Files/Television/Last Night's/Hacks (2021))/Hacks Season 1/Hacks.S01E04.D'jewelry.EAC3.5.1.1080p.Bluray.x265-iVy.mkv -> /mnt/My Files/Television/Last Night's/Hacks (2021) S01E04 D’Jewelry.mkv (ERROR: ffMPEG failed to create new file)
...

Seems I made a mistake uploading GTK Static for 2.3.12 - uploaded the correct one now. Please try that one.
(included the shared ffmpeg/ffprobe instead of the static ones by accident)

Note: this may not be related to the issue you're running into.

@hans OK it's working, not perfectly but working so I personally can live with it. Thanks

I dragged 3 files to it, correct names found in under a second, on clicking rename did so without issue. tried a couple of other files and took about 3 minutes to grab the right noame, but on clicking on rename did so without issue. Like I said I can happily live with it.

That's good news! 😊 

How is detection speed when disabling ffmpeg and ffprobe (in settings)?
Just wondering if that causes the delay.

@hans those I always have unchecked, but I just unchecked "Recursively search directories when add". Doing that and dragging the 7 or 8 shows to RMTV worked. One took a bit long than the others, but I believe that was because I hadn't dragged any episodes of it to RMTV yet.  Now on two of the files RMTV moved the NFO files to my save location as well.

EDIT:

Unchecking "Rename files starting with the same text" fix the NFO files being renamed and copied.  Just tested with 9 files and all populated in just a couple of seconds and renamed without issue.

@cccp64 Yeah finding similar named files can be slow, as it has to do some more work by getting all files and finding matches. Should not be slowing down things when comparing, but retrieving can be slow especially when a directory holds a lot of files.

Sounds like you're good to go though (correct me if I'm wrong). 😊 

@hans Yea it seems to be good now. I would make one suggestion and that is to somehow make as note about ONLY checking that box if you're new to RMTV and have files for a show that have not been properly renamed. Otherwise like in my case there is no legitimate reason for RMTV to search my files or rename like files. I'll check back in at the end od next week to make it official one way or the other on how RMTV is behaving. Thanks for the help and input, as always very much appreciated.

Thanks for the suggestion. Just wondering: do you have a lot of files in those directories? and/or is it on a network share?
Just asking since, on my Mac anyway, it doesn't show a noticeable slow down. 

No, but now that you mention it since by rights it should only be searching the folder and any sub-folders it has it shouldn't take but a couple of seconds. It's not like I'm pointing it at the entire Torrent folder or TV Series folder just at a single folder with the episode in it and no sub-folders. I wonder since with drag and drop if it's not trying to search everything since at that point I'm not actually pointing it to a folder. Not trying to beat a dead horse but this is where proper logging comes in handy. Better to have individual logs for apps rather than having to sort through the mound of info in system logs.