M’gladbach vs. Man City Lazio vs. Bayern Atlético vs. Chelsea RB Leipzig vs. Liverpool Porto vs. Juventus Barcelona vs. PSG Sevilla vs. Dortmund Atalanta vs. Real Madrid
They should run off the CL like they did last year, postpone it until May and do it straight knockout on neutral venues with the potential of some fans.
Not even necessary to cancel the Euros. If the CL is deferred until the domestic season is over, then the domestic season should be concluded 3 weeks or so prior to that.
Pick a country like they did last year in Germany or Portugal and run it off there. The UK could be a good choice this time around with the vaccines.
Give the teams their bases and run it off like knockout international football. Single ties - weeks should do it as it’s only 4 games at most in 21 days.