OK, I found that page you showed me and will try it. It is the one that is only 77 mb but we will see what happens. I know Joe is leary of the small size. I am going to airdrop it to my other mac and d/l and see what happens. Thanks.
I downloaded the STP for Catalina on MacJUpdate and when it was done it said I needed Mac OS 11.0 (Big Sur) to open it.
I just d/l'ed STP via this link
at Download Safari Technology Preview for Mac | MacUpdate
, and while I didn't complete the installation, I got to the last step with no problems in Catalina 10.15.7. (The d/l'ed .dmg is 84.7 MB.)