Tantalum is primarily used in electronics to build power supply decoupling capacitors. It is considered a conflict mineral so it is a good idea to minimize their use or insist on careful sourcing.
Unfortunately, there is currently a worldwide shortage of MFCCs the alternative to Tantalum Caps. This recent article guides people towards choosing Tantalum substitutes:
This article argues for Tantalum Polymer caps:
Fortunately for most wearable applications the power levels used are such that MFCCs will be sufficient and presumably Tantalum capacitor use will drop overall in the near future.
This article has guidelines for design away from Tantalum: