If they upgrade to premium tier, set up your virtual server then. Your total cost, $0 for the duration it's free + $4 * the rest is still lower than $4 * lifetime, and the cost for switching is only going to be marginal.
Just look at all the people panicking with the free Google Workspace shutdown.
Cost of my time for reading contract and learning new proprietary tool is not worth it for several years.
Cloudflare is arguably better from big tech. But cost of deployment some binary package on confidential server, keeping up with their marketing bs, etc is simply not worth it.