Found this by googling the term Pauschalsteuer and using translation:
"requirements
To pay the flat-rate tax instead of ordinary taxes
Foreigners who
• have not exercised or exercise an activity in Switzerland 1;
• require renewal of the flat rate tax for the next tax period.
Swiss
• The first time in Switzerland residence or
• Return after at least 10 years of absence from the country, provided that: ◦ In Switzerland
◦ Have not been fully taxed in Switzerland for the last 10 years.
• The right to lump sum before the expiry of the tax period of the entry date (cantonal right) or before expiry of the calendar year (federal law) following the entry.
Double citizens according to the rules of returned Swiss citizens (see above) 2 .
1 Exceptions: voluntary activity, participation as a member of the board of directors with a fee of up to a certain amount, artistic performances for charity, a limited partnership with a Swiss limited partnership (KommG), writers or scientists who generate the intellectual part in Switzerland and exploit their work abroad (Safeguards necessary to refute the presumption of ordinary employment which excludes the flat-rate taxation, and the gainful employment of the spouse, insofar as their activity is not related to the current or former activity of the taxpayer abroad.
2 If only the wife and / or the children under parental authority have Swiss citizenship, the foreign taxpayer is still subject to unlimited lump-sum taxation."
https://www.pauschalsteuern.ch/voraussetzungen
Also this from back in 2015 - don’t know if it got passed though, but if so the OP might not qualify.
"In the Tiefsteuerkanton train the wind is turning: the cantonal council wants to tighten the rules for the flat rate taxation. On Thursday at first reading, it decided to raise the assessment bases. This means that the financially charged canton wants to take more tax in the long term.
The decision fell with 42 to 28 votes, whereby also numerous citizens voted for the tightening. However, the change is not yet definite. The second reading with final vote takes place in four weeks. The Council followed with the decision of the government, which also wants to increase the hurdles.
Foreigners must now have 11.76 million Swiss francs
A taxable income of 588,000 Swiss francs will be the minimum limit for flat rate taxation in the future. Previously, the limit was 420’000 Swiss francs. Moreover, under a taxable assets of 11.76 million, no foreigner can be taxed at a flat rate. Up to now the ceiling was 8.4 million.
By 2020 these new minimum amounts should only apply to newcomers. From 2021, however, they should also be applied to the existing flat-rate flights.
Too poor for flat rate taxation
Not all of the currently 104 concessional flat-rate taxpayers will be able to create the new hurdles: Financial Director Peter Hegglin (CVP) expects that about half will be completely eliminated from flat-rate taxation. In the future they will be too little wealth to benefit from a discount.
These 52 persons must be taxed as from 2021 as all other trainers. The canton therefore expects an annual increase of about 450,000 Swiss francs.
With aggravation still competitive
However, the prerequisite is that these persons do not move away. However, Hegglin was convinced in the debate that the canton of Zug is still competitive with this tightening.
Beneficiaries are rich foreigners, who live in Switzerland, but do not pursue any gainful employment here. A prominent example of train is the Russian entrepreneur Viktor Vekselberg."
http://www.handelszeitung.ch/politik…lsteuer-763990