Legitimate interest is the obvious way to not require opt-in and while I’m sure the regulators are getting tired of seeing ad networks claim that exception a router company claiming it for crash support seems like something that will likely be deemed in bounds. Especially if that company has made a good faith effort to show its not repurposing that data.
And yet, Article 32 (https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELE... the GDPR states:
Silence, pre-ticked boxes or inactivity should not therefore constitute consent.
Consent should cover all processing activities carried out for the same purpose or purposes.
When the processing has multiple purposes, consent should be given for all of them.
If the data subject's consent is to be given following a request by electronic means,
the request must be clear, concise and not unnecessarily disruptive to the use of the service for which it is provided.
There are several other basis as well including ‘legitimate interest’. You can see all of the basis in article 6(1).
If you use a different basis you don’t need to collect consent at all whether opt in or otherwise.
Hardware data from crashes used just for cause analysis and properly stored/secured is a fairly straightforward ‘legitimate interest’ argument.