For using WIFI this seems to work, but when using cable internet I am unable to ping the outside. Config of the third adapter: third: match: {macaddress: "08:00:27:e8:49:64"} set-name: "cable" dhcp4: yes

That was not part of your original question as stated in the main post. Have you checked your routing table yet? Which interface does your default route go through?

I do not understand what the routing table tells me.: default via 192.168.200.220 dev cas10 proto static default via 10.62.64.70 dev cable proto dhcp src 10.62.64.182 metric 100 10.62.64.0/23 dev cable proto kernel scope link src 10.62.64.182 10.62.64.70 dev cable proto dhcp scope link src 10.62.64.182 metric 100 172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 192.168.200.0/24 dev cas10 proto kernel scope link src 192.168.200.100

It tells you that you have two default routes, and it tells you that your primary default route goes through cas10 – which as you said earlier has no internet access, and which I said should not have a gateway defined for that reason. Remove the gateway configuration for cas10 if you want the 'cable' interface to be used for Internet.

I just followed your answer in which you do define a gateway for that cas10 adapter. It seems your answer is incorrect/incomplete. I'd appreciate if you could add that gateway explanation to your answer. I am very new to networking,

You insisted that I read the questions provided before answering them, and that's what I did – I answered according to the information provided in your question, and in the question you have a Netplan configuration that has a static address and gateway on one interface and DHCP on another (with no mention of a third cable interface, at that). Now I will insist that you read the answer that was provided – in the 3rd and 4th paragraphs of the 2nd section of my answer I pointed out that the interface should not have a gateway defined if it doesn't have Internet access.

I don't mind explaining networking basics, but I do mind when someone sets hard rules and then changes them after the fact.

I am not so sure what you are complaining about.

Please explain

I am not quite sure what a gateweay configuration in a netplan changes, or why you define a gateway

You said "I just followed your answer in which you do define a gateway for that cas10 adapter.". There is no cas10 adapter in my answer, and there was no cas10 adapter in your original question, and indeed your question did not specify at all which interface has Internet access and which one doesn't – is it the static interface that provides Internet? is it the DHCP one? This was not specified, so it was impossible to answer for that.

In that sense I am unaware what that "gateway" change in my question

In fact the only reason I even thought to bring this up is because your other posts mentioned something about one of the interfaces being used for a single device only.

I am unaware of the details of the information required. You could have asked me

I am not an expert in networks

Yes, but if you try to set strict rules about the way I should answer, you don't change them after the fact.

Yes yes you get your 300 points. Don't you worry!

I absolutely don't care about points. That's not why I post on this site.

I will ask probably much more questions, like what is the effect of definign a gateway

(Not surew what rules you mean)

Why did you delete your answer?

Anyway, thanks for your answer and your additional input ...