I've completed the process of transferring 2x Roth IRA and 2x Trad IRA accounts from Vanguard over to Robinhood. It took a bit more time/effort than expected, but overall it was an easy $18.6k.
I started with a trial run on our smallest account. I called Vanguard and asked them to convert my VTSAX mutual funds to ETF equivalent (VTI). That was pretty easy, and a day or two after it processed I initiated a full account transfer from the Robinhood side. That transfer ended up getting rejected. After some digging, I realized my cash settlement fund at Vanguard was set up to use some sort of mutual fund, so I converted those to a cash equivalent. Checked on it a few days later, and there was still a small mutual fund holding...after some time on the phone with Vanguard, we figured out there was a lock that was put on my account after the first failed transfer. Got that sorted out, and then re-initiated transfer from the Robinhood side. Everything transferred over within a week, except for fractional shares which were then automatically sold and swept over as cash another week later. Repeated the process with remaining accounts. Had one that was rejected the first time...I think I may have started it before the VTSAX to VTI change was finalized. Submitted one last time, and now everything is complete.