Any recommendations?

I have Sequoia running great so far on a 2017 i5 iMac with 24gb ram. Is there anything this could run past Capitan? My goals are just 1) nostalgia, it was a beautiful machine in its time, 2) it serves as backup for media. I’m really just looking to be able to run a usable web browser. I should also note that the HD died long ago and I have Capitan running on a newish external usb hard drive. Capitan runs well itself but no web browser works for most sites. Thanks!