On the list trainline gives it doesn't mention euston as having a ticket station
If the Trainline list you're looking at is this one or similar:
"How do I collect tickets from a self-service ticket machine?"
then Euston is in the list but under the name "London Euston".
Note that the ticket machine will ask you to insert the payment card used to purchase the tickets before typing in the booking reference number, so you'll want to have both on hand. (There are cases where you can get away with inserting a different card, but if you are able to use the same card -- and as long as it's not a numberless card from Chase Bank -- then there's nothing to worry about.)
Also since trainline aren't clear on who has ticket stations where do I find out who has ticket stations or not, also are ticket stations for all tickets?
The official source is probably National Rail Enquiries, where you can find separate information pages for each station (which show, where available, "Collection of pre-purchased tickets: Yes, from ticket machine"):
https://www.nationalrail.co.uk/stations_destinations/default.aspx
(Official does not necessarily guarantee correct, though.)
I think you can safely assume that all main stations in London have ticket machines.
All National Rail train operating companies and all ticket-selling websites use the same system for passengers to collect tickets from the station (called "Ticket on Departure", TOD) so you can use any ticket machine to collect your tickets, regardless of who you bought from and whose machine it is (unless the machine cannot do TOD at all - I don't know how common that is?). (London Underground is not included, so you can't in general collect train tickets from Tube stations.)
Although the Trainline app doesn't automatically say that you can collect from your origin station (Euston in this case), when I search for a journey from a station without ticket machines and select "Collect from station", it does automatically show the warning "X does not have a ticket machine, you can collect them from another station". So if you don't see this warning when selecting "Collect from station", then it should mean that you can collect from your origin station.
You also don't have to collect the ticket at the station you selected.
It seems that Trainline doesn't ask you to select a station for collection anymore.