In some cases it gives a float

[osiixy]

multibootusb/scripts/mbusb_gui.py

Line 323 in fa89b28

self.ui.slider_persistence.setMaximum(config.persistence_max_size / 1024 / 1024)

To replicate the crash you need to select the destination partion and the ISO (in my case: tails-amd64-4.25.iso).
My solution is to force conversion to int.

Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/scripts/mbusb_gui.py", line 286, in browse_iso
    self.ui_update_persistence()
  File "/usr/lib/python3.10/site-packages/scripts/mbusb_gui.py", line 303, in ui_update_persistence
    self.ui.slider_persistence.setMaximum(config.persistence_max_size / 1024 / 1024)
TypeError: setMaximum(self, int): argument 1 has unexpected type 'float'
Aborted (core dumped)

solution:

self.ui.slider_persistence.setMaximum(int(config.persistence_max_size / 1024 / 1024))

That's all.