Desktop Client App (Offline Work)

Has there ever been any discussion to have an ability to produce invoices and quotes if the internet is down? Im in california and power outage is affecting my internet but my clients customers in other states still expects production.

How do you want to transfer the created Invoice without electricity?
Just set up the Application to a CloudServer which is not affected by PowerOutage and then access it via mobile internet as mobile internet is mostly not affected by power outage aswell.

But to be clear: no there will be no desktop app which also makes 0 sense as without power you cant even run a Computer, also if you run it on a Laptop you still cant transfer the Invoice to your Client without power.

Your Power Outage problem is nothing that InvoicePlane have to solve nor I want it to solve. IP should focus on what IP is made for, not solving problems of govermental stupidity to set up proper electricity regulation.
Solve the problem by its roots: your electricity regulation.

For me iots a clear downvote (but I cant downvote)

Btw: if you want to go for a Desktop App for creating Invoices and Quotes, there are sooo many programs! Just google it

I wasnt detailed enough.

My production version is hosted somewhere in cyber world (1and1). To use it, my client has an ISP routed to a home office network of three computers. His office had electric but not the isp. His home office is not in a good location to turn his phone into a hotspot and the computers do not have wifi capability.

So…my thought is i could create a localhost on the office server pc so they can work offline but that will need to be bridged to the production server for when the isp comes back up

Ah, now I know what you mean.

Well setting up InvoicePlane on Localhost (XAMP/WAMP) etc should not be the problem, but syncing it to the other Server is not possible out of the box.

Maybe it will be the case for IPv2 but I dont think so. But now I understand this Request!
If enough people will vote for it and the devs see it as a part of IPv2 it may will be included in v2

Instead of looking at InvoicePlane features, you should look into replication server features for MySQL.
That would allow to have a master server (say the 1and1 server) and a slave server (say the local one). Then when there’s an outage, the slave become master and the master become slave. So when 1and1 server is accessible again, the replication will copy the data processed locally to the 1and1 server. Once done you switch back the master and the slave.
It is also possible to create a replication master-master … but a bit more tricky.

For more info, read MySQL doc : https://dev.mysql.com/doc/refman/8.0/en/replication.html

Thank you CF, good to know and worthy of deliberate research.

You can go with local web server as @M4rt1n mentioned.
You can use Raspberry Pi for web server + you can run RPi on battery pack for phones.
There are also prepacked images for RPi with LAMP
RPi zero W is small and cheap and have enough power to run.

Alternatively I would suggest to use a UPS for your main router/network, so if you get power outage you are still connected (I use UPS to run home network when power is down).