Ditto for PA Semi, who were bought by Apple.
SiFive changed to being an IP provider, is no longer selling chips.
It feels sometimes like the PC world is in collapse. No one wants to sell chips any more, it's all for cloud or for appliance-ized phone-lile systems. When someone does come along and starts making new chips, they get bought.
I wish the hyperscalers had some interest in keeping a competitive market alive, in supporting independent competition. I respect the desire to have a strong in house team and Graviton 3+ have really been excellent (Nitro is also super interesting deep tech I wish we saw in the world; alas AMD's SeaMicro acquisition took one similar out in the wild super-fabric offering off the table rather than promoted it). But man, the consolidation in chip making has been brutal & it doesn't feel like there's enough folks getting started making cores to keep things healthy. There's some disruption from below with RISC-V starting, but it's been slow & is very down market still (Tenstorrent being the notable exception). The broad ecosystem feels like it needs help, needs new vitality, is ossofying, in large part because of these acquisitions.
Alternatively, smartphones are the PC (personal computer) of choice.
SoC and mobile chips are themselves near desktop level performance. Heck, Apple's A18 can outcompete the M1 in certain benchmarks, and outcompetes a Kaby Lake Intel i5 (2017-19 period) in most aspects.
We are reaching a point where commodity mobile processors have mid-2010s desktop chip level performance but at a fraction of the cost, which opens up plenty of opportunities.