My tips might not be so good for the change away from the recent lots-of-quality-time schedules our birbs have all been able to enjoy. This is more for going-forward once the re-set of reality has been established:
When I got my budgies I quickly upgraded and then re-upgraded their cages to larger and larger sizes. Same for my conure. (My Petco's Bird Whisperer calls the cage I got for my Sunny the "Conure Taj Mahal.") The reason for this was because they would be stuck in their cages while I was at work and I wanted them to have as much safe space as possible.
Now while I work-from-home, I still keep Sunny in her cage if I am not present but the budgies (specifically Jefferson) were Already Negotiating for NO CAGE restrictions (basically, by refusing to return to cage in the daylight) well before we went to work-at-home.
Anyways. What I would do was turn Off the TV when I left for work, and Put on Classical Music Station on Radio.
IF I was only leaving a Few Hours, I would put television (youtube via Roku tv) a video of an Aquarium with "relaxing" music.
(Make sure to choose video a long, multi-hour video with No Yellow Lines in the video timeline - that is where they can interject sudden loud scary commercials!) The reason for aquarium is, there are really No fish that Budgies react to as predators. Whereas even a beautiful-landscape video could occasionallly send the budgies into a panic - I assume perhaps there was a predator-shadow or -call that I could not perceive.
HOwever IF i was gonna be gone All Day I would NOT leave the TV on. I would put classical radio instead. Two reasons: (1) it is fairly calm, yet auditorially interesting. (2) I don't hate it (in case they were to imitate) BUT - I don't really like it so I will automatically Turn It Off when I am home, at least after a short while. (Whereas I might leave the aquarium video running.) SO the birds know For Certain if I put on the Classical Radio I WILL be Gone for 8+ hours.
I have at times left and only put on the aquarium and then I was gone for MUCH longer than I expected (more than 6 hours) - and they were clearly unhappy and stressed by it. Whereas on the Very Few occasions where I put on the Classical and then returned home a little early, they were obviously surprised but, until seeing me, had clearly been happy and relaxed.
I suggest implementing some such procedure. It will undoubtedly take them a little while to adjust, but, this can certainly help.
And also of course make sure they have the biggest cages you can manage, when you are going to be leaving them alone all day.
