My experience has been that for Linux you are always better buying older mid tier hardware because all of the issues and optimisations have already been worked out and those changes have flowed through to your distro so you aren’t waiting on kernel updates.

I've switched my gaming PC last year to Linux and it's been flawless.

Originally ran a 3070 which matches your "older mid tier" description and then upgraded to a 9070XT maybe 6 months after launch so not so old or mid-tier.