JanetheWriterHey @JanetheWriter -- Good question, here's a partial list of pen brands to reference:
YES - Int'l Standard: Caran d'Ache, Faber-Castell, OHTO, Kaweco, Pelikan, Schneider, Waterman.
NO - Proprietary/Other: Cross, LAMY, Parker, Pilot, Sheaffer, Platinum.
All three have proprietary cartridges, but Platinum has an adapter available: http://www.cultpens.com/i/q/PT21607/platinum-international-adapter
Edit: apparently you might be able to squeeze them onto a Lamy, but it's (literally) a stretch: http://www.fountainpennetwork.com/forum/topic/146902-lamy-safari-cartridge-compatibility/
YES - Int'l Standard: Caran d'Ache, Faber-Castell, OHTO, Kaweco, Pelikan, Schneider, Waterman.
NO - Proprietary/Other: Cross, LAMY, Parker, Pilot, Sheaffer, Platinum.
Lamy: No, you have to use the proprietary cartridges. http://www.jetpens.com/search?q=lamy+cartridge&v=2 https://www.penchalet.com/ink_refills/fountain_pen_ink/monteverde_lamy_cartridge_fountain_pen_ink.html
Platinum: No, unless you get a cartridge adapter. Then you can use these Private Reserve cartridges. https://www.penchalet.com/pen_accessories/fountain_pen_converters/platinum_cartridge_adpater_fountain_pen_converter.html