I used to do weightlifting, but it's hard to keep up daily discipline with potential injury risk. Rest days are mandatory and this is the #1 killer of compliance over time (for me).

Rowing is my go-to now. It is low impact so I can do it every day without any exceptions. I've been able to hold onto this discipline for 2 years now. The advantage of rowing is that there isn't really a limit to how much it can suck. You can burn 500 calories per hour, or 9000. It's more of a psychological battle than a physical one.

My system is to row at whatever intensity and duration until I my brain starts to internally play music from Spotify. However long that takes. Sometimes it's 40 minutes, sometimes it's 80. I think this variance mostly boils down to blood sugar and what I ate the previous day. If I gorge on a box of snacky crackers, I need to row for at least an hour before I stop feeling like shit.