@VoluptuaGoodshag I feel your pain on the adjustment.
I was self-employed for years so I'm used to working from a quiet empty home (and well as work commitments that take me out of the house). It is just such a difference having another person around all the time. Someone asking where I'm going if I'm putting on my coat - which is of course reasonable, but takes some getting used to when I have just been able to 'go out' for 20 years. dh is big on the outdoors but a lot of that is weather / season dependant. So yes, there are times when he is standing around... sort of expectantly, hoping I'm going to magic up something interesting and fulfilling.
After a full on career which hindered dh's desired holidays and limited his outdoor hobbies, he was very clear that he did not want to take up a 3-times a week golfing commitment, or get over-involved in volunteering. He wanted the flexibility to be spontaneous when the conditions are right for his sporting activities. That is great but he knows he also has to be responsible for sorting out his own down-time. And he has a group of friends who meet every week.
You asked for practical ideas - so here are mine:
dh is very easy going (and we are genuinely very happy together). If I ever suggest going somewhere or doing something (a walk, a picnic, out for lunch, trip to the theatre, a foraging experience etc) he will happily and enthusiastically join in. But I am very clear that I make these arrangements when there is something that I want to do, I'm not taking on the mental load of filling his time. It's the same kind of benign neglect with which I used to be a parent - leave them to get bored and they'll find some way of occupying themselves.
Managing and adjusting over time takes good communication and clarity on your part. I have been clear that although I love cooking and happy to plan and make dinner almost every evening, I will not wait on him hand and foot, or organise my day around him and he remains responsible for making his own breakfast and usually his own lunch. Who knows maybe in another 10 years we'll be sitting down together for breakfast every morning, but that doesn't work for me now.
We also have our own spaces in the house where we can keep our own mess and retreat to. Our previous 4 bedroom house is now a house with 2 bedrooms and 2 'offices'. That is a lovely to contrast to a 6 week holiday where we spent all our time together in a very small space, and still got on great.
I still do a little work, and I also have friends who I meet during the week for a walk or a chat, or fur lunch, and a few regular hobby classes. We have a shared calander where I write down anything that affects us both - e.g. visitors, commitments with couple friends or family, times when I might be away overnight, events that are booked for both of us, activities with our dgc etc. But I don't write down everything that I plan to do alone. At the start of each week we have a chat about what is on and I fill dh in then about my yoga class or a work meeting, or time just me with my friends. even after 2 years of retirement dh stills seems surprised that I have such a busy life 