What type of oscilloscope can be used to troubleshoot 100BASE-T1 automotive ethernet?
Sounds like you want a protocol tester more than you want an oscilloscope.  But oh well, that's not the question here.

I was told that in order to troubleshoot and test on this standard, the scope must be capable of 1 GHz

No. Even wikipedia will tell you that it only requires CAT3 cabling, and that doesn't guarantee a bandwidth even close to that.

Ah, with your comment:

Only looking for network traffic analysis at this point

yeah, well, then an oscilloscope in itself is no use at all. You'll need a device that speaks that protocol. For some higher-end, there might be add-ons that implement such a protocol decoder. But that again has nothing to do with the scope's 1 GHz bandwidth or not – it's something that extends the signal processing capabilities of the scope, and &quot;converts&quot; it into a protocol analyzer.
Since this is an ethernet standard, in principle, a network card connecting your device A to a PC, which sniffs and forwards the packets in both directions, and another network card for PC &lt;-&gt; device B would sound like a saner investment than an oscilloscope.