There are some sites where I've tried fully whitelisting them on uMatrix, and that's enough--so I give them a dedicated Container Tab and use it that way. But there are others where even with uB0 and uM completely disabled, the site still refuses to let me sign in. I'm not sure if it's some combination of Firefox's built-in tracking protection, or the fact that I'm coming in through a VPN, or what: but at some point, rather than spending a half hour fighting with it, just signing in on my phone was easier.