"No linear SOA" as in, no DC (linear operating mode) SOA curve at all, or if there is one (I forget if I've
ever seen a DC curve on an IGBT), it is tiny, a small fraction of the total power rating.
MOSFETs are available up to 4500V -- with pretty reasonable ratings at that, too* -- I'm not sure where you're finding "a few hundred volts maximum".
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif.pagespeed.ce.5xOqKkq0Co.gif)
*I used to observe that, heater power aside, vacuum tubes still held their own in this one domain: at high voltages and modest to very high powers. For example, a 6LQ6 horizontal output tube might have a saturated plate "resistance" of 70 ohms, and a peak voltage rating of about 7kV (strictly under cutoff conditions, mind). The heater and screen power requirements make overall efficiency rather worse of course (about 20W between them, plus a plate dissipation rating of 30W), nevermind the requirement for two extra supplies (heater and screen), plus a fairly large grid voltage (about -200V is recommended in peak cutoff).
Over the last 5 years or so, MOSFETs have been released with ratings around 2500V 10A and 4500V 2A (30 ohm?), completely removing any claim tubes might've still held in this domain.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
(Vacuum tubes for high frequency (klystrons, TWTs, etc.), high power (some industrial and radio finals; magnetrons, etc.), and various physics and research applications, still dominate those fields. Of those, TWTs are probably the next to fall: they've been flying on satellites for literally as long as satellites have been flown in space, and are extremely well understood, reliable and still perform quite well despite their old fashioned nature. However, microwave transistors -- Si LDMOS, GaAsFET, PHEMTs and GaN FETs -- have been in commercial use for many years now, and it's my understanding that some are finally getting rad-hard and space-ready approval..?)
Ahh... I digress. Fun stuff.
Tim