

Check this out, not sure how relevant, but a cool project that unlocks some of the proprietary functionality of a bunch of Scarlett devices on Linux: ALSA Scarlett Control Panel
Also if you haven’t checked it out already, r/linuxaudio has some posts I found on various Scarlett device questions, you’ll have to search for specifics.
And lastly, are you using Reaper as a Flatpak? If you are, download “Flatseal” it’s a Flatpak app that allows you low level control of all your flatpak application permissions on your system. You can set all kinds of low level system access to the Flatpak you’re using, that can help fix various issues that come up because of how Flatpaks are sandboxed on Linux.
Hopefully some of this is helpful. I’m not an audio expert, so my abilities on this issue are limited sadly.
Install the latest version and then use their upgrade utility when they announce it on their official blog. Upgrading versions is easy, takes a little while, especially on an old system like yours, but not hard at all.
Mint is my favorite “Just works” distro, enjoy!