In order to remedy the situation with the faulty USB-hubs in the various monitors I have tested, I bought a Belkin Pro Thunderbolt 4 Dock. It can do 5k2k @ 75Hz which is what I need for my day to day use, but it’s a shame that I had to purchase such an expensive docking station on top of an expensive monitor.

Nevertheless, the dock has served me really well for the past couple of weeks and if you have the money I’d recommend the Dell U4021QW together with the dock. All in all, the Dell is a nicer monitor than the Lenovo.

Edit: This does not solve my original problem (one monitor -> two computers sharing peripherals). Luckily, I have moved to a house where I can have a big enough office to justify having two desks: one for my work station and one for my gaming setup. Hence, I will simply have the thunderbolt dock for the laptop peripherals and switch between laptops using the TB4 connection and use separate peripherals all together for the gaming computer.