Not 100% the same as a 17 year relationship, but I had a live in boyfriend do this before over covid.
All I have to say about the manner in which it was done was cowardly.
Like you, I got a text when I was at work, effectively dumping me through text then saying he was going on his lunch break to collect his things.
I panicked and told work I had an unexpected emergency to get home to. I didnt want to leave him alone in MY home to take whatever he needed then go away to god knows where. I especially wanted to make sure he didnt take our dog (which he gifted to me).
His work was a lot further away than mine was to my house, so I made it home before him.
No tears from him, he just went round packing his bags as if he was going on holiday. He had informed his family so he could get more bags and boxes etc and he made sure he got every last item so he didnt have to come back. I sat there in floods of tears, in absolute shock at what had happened (as everyone believed he was close to proposing as asked my mum for ring size weeks earlier)
It took a long time to get over this break up. And in fact, we turned into a FWB situation a few weeks after because I felt too weak to walk away completely, which only prolonged the pain.
Make sure you look after yourself and give yourself time to cry and grieve properly.