Could the router be put into operation in the meantime?
I would be interested to know if the Yallo Cable Box uses IPv4 with DHCP on the LAN.

Yes, I think this router can do that. Actually, it can do almost everything. It can also do vpn, DNS, DHCP, routing etc.
If you know what you need and how to configure it, it can do that. You can set it via console or via the web interface.

I don't know the Yallo Cable Box, but I assume that IPv6 is only used on the Internet side, because according to their instructions for WiFi adjustments (https://support.yallo.ch/hc...) you are supposed to access the web management of the Yallo Cable Box from the internal network via 192.168.1.1, which is a perfect IPv4 address.

It can therefore be assumed that the Yallo Cable Box uses IPv4 as normal in the LAN and that the MikroTik hEX would basically work. The hEX has a configurable firewall, BUT if you have never worked with MikroTik before, you are in for a steep learning curve and possibly many days of work!

I use the hEX S myself on another provider's cable modem and have used it (and other MikroTik switches and access points) to separate the home LAN from the home office LAN.

Personally, I really appreciate MikroTik's inexpensive, small all-rounders, but I had to familiarise myself with MikroTik's own logic and terminology over a period of many weeks. There is a large English forum where, however, you can often only recognise and circumnavigate the half-truths after a few failed attempts.

If you don't want to deal with the command line and are looking for a simple, quick solution, then MikroTik hEX is not for you.

If you still want to try it and know something about IP, DNS and DHCP, then a pragmatic solution could also look like this:
>> Buy 2 pcs. MikroTik hEX and connect both separately to the Yallo Box via their integrated Internet/WAN port using a cable. Then connect your computer via cable to one of the LAN ports (2-5) of the hEX and configure the MikroTik router via the rudimentary web-based installation wizard "WebFig" (https://systemzone.net/mikrotik-r...) using the MikroTik default IP 192.168.88.1.
Then connect the home devices to ports 2-5 of the first hEX and the home office devices to ports 2-5 of the second hEX. The two hEX routers then take over routing, DHCP and DNS for the devices behind them and separate them from each other.

My suggestion above is not very elegant from a network point of view, as you can solve everything with one device (but with a steep learning curve), but in view of the low prices of the MikroTik hEX, it may be worth considering from my point of view. Before buying, please read the linked instructions for the first installation. If you only understand "station", it is not for you...