I've used a lot of good printing enhancers/enablers in Firefox. But Print Edit WE is by far the best for stubbornly printer-unfriendly (or print-to-pdf unfriendly) pages. It may take a bit of experimentation, but Print Edit WE's capabilities are amazing. I am on Firefox ESR, which is currently based on version 78. Hopefully ESR's upcoming update to a Firefox 90-based version won't break any of Print Edit WE's capabilities.