I wish he was Prime Minister. But sadly he doesn't see a Lab/Lib/SNP coalition which I think is the only way.

Jeremy Corbyn rules out alliance with SNP before 2020 election
Join my crusade and let's lead Labour to Government, writes leader Jeremy Corbyn "we’re not looking for an alliance with the SNP"
No Labour pacts with other parties, says shadow minister

I'm sure I also saw an Andrew Marr interview with Jeremy Corbyn where he said that he was not in favour of forming alliances with other parties.

Hopefully he will change his mind. I can't see Labour winning outright and I feel a cap on his more extreme left policies would be needed. I see no reason to doubt he'd be a good Prime Minister (except for media hatred). But he needs partners to curb excesses. And the SNP are the voice of Scotland and deserve a voice in Brexit (May has denied them one).

According to an article published today, Jeremy Corbyn is still against a cross-party alliance, as are the Lib Dems.

Labour and Lib Dems reject Greens' call for electoral pact against Tories
"Corbyn, who has previously expressed opposition to the idea, ruled out any pacts with the Greens or Lib Dems, or the SNP, at a meeting of Labour’s national executive committee on Wednesday, a party source said."

I cannot see how a Labour/Lib Dem coalition wouldn't benefit both. A guaranteed soft Brexit with Single Market retained plus Customs Union; better immigration; boost for NHS and benefits and education. Labour agrees not to fight seats where Lib Dems could beat Tories; ditto Lib Dems on seats that Labour could beat Tories. SNP would be delighted if Corbyn more favourable to Scottish soft Brexit. It works for all - except Typhoid May.