Longish distraction for large dog while I WFH, non-food?

I have recently moved out of a multi-human home, and my 10 year old collie thinks this means I must actively play fetch or tug with him at all times.

This is obviously not possible while I am attempting to work from home, but I feel bad for rejecting him so often, and he's obviously bored. I have never been his only human in a home before now (although I've always been his primary human), so this has been a difficult adjustment for us both.

• It needs to be something I don't actively participate in so that I can work.
• Anything food related, even frozen kongs, ect. he finishes in mere minutes, 15 mins max. Food puzzles, etc. are no match for him. (I also have a small dog, and frankly they are both chubby already.)
• I can't afford to pay for a walker/babysitter/doggy day care regularly.
• I also cannot simply take him on multiple walks per day in this heat/humidity due to health issues. (Walks will resume when the weather cools down, hopefully soon!)
• He won't really chew on toys by himself. I have tried to get him dozens of toys, and either it becomes a safety hazard or he thinks it's a fetch toy and just brings it to me. He LOVES the nylabone wishbone things, but the plastic gets rough and tears up his gums, so I've stopped buying them.
• I have often considered an automatic ball launcher, and I did just order one, but he throws a tantrum if he doesn't have 101% of my attention when I'm playing fetch with him, so I fear that he won't be interested.

Does anyone have any suggestions for things to keep him busy and entertained BY HIMSELF, no human involved?