Nuumobile A7L GSI build

Hi. I have a Nuumobile A7L that I’d like to put a GSI build on. It’s Treble (comes with android 10), with VNDK 29.0, but A only (not A/B). It’s not on any TWRP lists, so I have to use fastboot. When I try fastboot erase system, it says partition table doesn't exist. Is TWRP available? Is there another fastboot command?

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Fixed. Needed to be in fastbootd.