I wanted to solve this problem once and for all by reaching out to the Bigger Pockets community and seeing what platforms, techniques, or methods other landlords/PM's use that works for them.

Nestegg.rent has a rent collection platform.

To your point about the MH and titling, from what I can tell the county tax records reflect this property as a "Mobile with Land".  

I use Zoho CRM for my investing business since it's industry leading, completely customizable, and under constant development to stay ahead of the feature trends.For my agent business, kvCORE is an all-in-one CRM & Lead Generation platform provided for free by my brokerage.

You’re right in that there is no app, but the browser version is optimized for mobile and keeps you logged in, so I don’t mind it at all. 

Also check where you have it posted for rent as different online platforms are popular in each area.

I use DocuSign to create fixed term leases for my mid term rentals but these rentals do not originate on any of the STR platforms. 

Branch out and get on every platform that you can, with the ultimate goal of taking only private bookings from repeat guests....But yes, everyone here is probably a Premier Host or Super Host.

You can do it yourself by contacting the local secretary of state (typically), hire an attorney, or use platforms like legalzoom.

I have a project management platform that I use with my clients so I can be more organized with the tasks that needs to be done and with timeline.You will definitely want someone that knows development to handle your books.