Without paying you need to use the rolling / nightly iso.

VyOS is very good. It’s a fork of Vyatta which was sold to brocade and sold again to ATT. Ubiquiti products use a fork of Vyatta as well (EdgeOS on their edge routers for example). I used to work with Vyatta and Brocade so I was a big fan of the Edge line for home and SMB. Since Ubiquiti shelved EdgeOS and stopped putting meaningful updates out I switched to VyOS rolling on my home router with one of those Beelink mini PCs with dual nics.

There are rack shelves designed for this, I have been to production DCs that had rows and rows of servers on shelves. Just check the weight ratings. These servers are not designed to be mounted by their ears like switches. The proper rails or shelf is the solution here.