There are many ways to skin that particular cat.
I see lots of folks using variations of this homemade dealy: https://community.home-assistant.io/t/fsr-the-best-bed-occupancy-sensor/365795
I however have a SleepNumber bed which heretically has a cloud integration in HASS that provides an impressively accurate presence sensor for both sides of my bed.
If I were to get a new bed I might build my own, or consider the Withings Sleep Mats - https://www.withings.com/us/en/sleep/shop which should just work with the HASS/Withings integration. The Sleep mats are too expensive in my opinion though I really like my Withings Smart Scale.
Damn good bot!