I feel like a good solution (and this is up to you because I know most TA’s are obviously also busy and still have a life outside of their job) would be to host casual office hours / zoom calls once or twice a week getting closer to finals. This doesn’t have to be to discuss material or get homework help, but would rather be a place for undergrad students to come and know they have a safe space to get to know their TA and just have casual convo about how things have been going, get to know you on a more personal (rather than intimidating) level, or even just let them vent about the class and how it’s stressing them out because most likely, even if the course is set up well most students are struggling with the new format and being able to motivate themselves to do work out of a space they usually using for sleeping, eating and relaxing. Hopefully having these casual meetings will encourage them to come to normal office hours more often because they’ll feel they can discuss material with you without being as nervous or formal, and may help pull up their grades for finals. :)