There is no alternative to BlackBerry HUB.
I am currently testing Android Q. As the HUB+ services don't run very smoothly in this beta build and Liam&Co do not respond to the bugs reported in my other thread (last year they responded very quickly that they will address that), I am fearing that BlackBerry is moving down their activities with the HUB+ services.
This in mind, I was looking for alternatives to the HUB+ services. I tried nearly every mailing app for Android and there is no solution even near the HUB+services.
So BlackBerry please continue developing this great software package! I am willing to pay double the price if this is necessary 😉